计算:①y7x÷(-2x)②a-2a-1-2a-3a-1③12m2-9-2m-3④x2x-1-x-1.-数学

题目简介

计算:①y7x÷(-2x)②a-2a-1-2a-3a-1③12m2-9-2m-3④x2x-1-x-1.-数学

题目详情

计算:
y
7x
÷(-
2
x
)

a-2
a-1
-
2a-3
a-1

12
m2-9
-
2
m-3

x2
x-1
-x-1
题型:解答题难度:中档来源:不详

答案

class="stub"y
7x
÷(-class="stub"2
x
)=class="stub"y
7x
×(-class="stub"x
2
)=-class="stub"y
14


②原式=
a-2-(2a-3)
a-1
=class="stub"a-2-2a+3
a-1
=class="stub"-a+1
a-1
=
-(a-1)
a-1
=-1;

③原式=class="stub"12
(m-3)(m+3)
-
2(m+3)
(m-3)(m+3)
=
12-(2m+6)
(m-3)(m+3)
=class="stub"-2m+6
(m-3)(m+3)
=
-2(m-3)
(m-3)(m+3)
=-class="stub"2
m+3


④原式=
x2
x-1
-
(x-1)2
x-1
=
x2-(x2-2x+1)
x-1
=
x2-x2+2x-1
x-1
=class="stub"2x-1
x-1

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